In order to improve the safety of double-hole parallel underground tunnels under seismic effects, the influence of tunnel spacing on the seismic response of double-hole parallel underground tunnels is explored in this paper, aiming to provide a reference for the engineering design and construction of such tunnels. In this paper, taking the site in Tianjin area as the research background, the seismic wave processing software GM-Tools and EERA were used to perform amplitude modulation operation and bedrock inversion operation on the acceleration time-history data of natural seismic waves. The ABAQUS numerical models of double-hole parallel underground tunnels-soil mass with different tunnel spacing were established based on the dynamic infinite element artificial boundary theory, and a comparative numerical simulation study was carried out on the displacement and stress response under the action of the bedrock seismic waves. The results of the study show that when the tunnel spacing increases from 1.0D (D is the outer diameter of the tunnel) to 2.0D, the peak value of the horizontal displacement of the tunnel, the peak value of the maximum principal stress in the tensile zone of the tunnel lining, and the peak value of the minimum principal stress in the compressive zone of the tunnel lining show the trend of rapid decline, with the decreases of 83.3%, 62.5%, and 37.5%, respectively. When the tunnel spacing is larger than 2.0D, the effect of the tunnel spacing on the seismic response of double-hole parallel underground tunnels is not significant. In the design process of double-hole parallel underground tunnels, it is recommended that the tunnel spacing should not be less than 2.0D in order to avoid accidents such as tunnel fracture and lining leakage caused by excessive horizontal displacement under seismic effects.